/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode* dummy = new ListNode(0, head);
        ListNode* fast=head;
        ListNode* slow=dummy;
         while(n)
         {
            fast=fast->next;
            n--;
        }
        while(fast)
        {
            fast=fast->next;
            slow=slow->next;
        }
        if(slow->next)
            slow->next=slow->next->next;
        head=dummy->next;
        delete dummy;
        return head;


    }
};